I'm not entirely sure what you're asking about here. Helper classes are just a term people give to classes that are used to assist in providing some functionality, though that functionality isn't the main goal of the application. They're also used to reduce the amount of redundancy in your code. For example, reading some information from a cookie is somewhat tedious, but it's use may be common across all servlets/actions in your app. It makes sense to write a new class to handle that, so you just write one line of code in your servlet to get this other class to handle it for you.

That's just basic programming techniques...you don't want to replicate code throughout your app. It leads to more bugs and makes your app difficult to maintain.

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